Simple import in python 3 errors with complaint about bytes

Ian Kelly ian.g.kelly at
Tue Oct 21 01:48:23 CEST 2014

On Mon, Oct 20, 2014 at 5:29 PM, Mike Boyle <moboyle79 at> wrote:
> I'm modifying an extension written with the c-api to have a datatype of quaternions <>, with one of the goals being python 3 support.  It works nicely in python 2.7, but for python 3.x gives an error that I can't find anywhere on the google.  The directory looks like this:
> .../site-packages/
>     quaternion/
> contains a line like this:
>     from .numpy_quaternion import quaternion
> But when it hits that line, python 3 throws its hands up in disgust:
>> python -c 'import quaternion'
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
>   File "/Users/mynamehere/.continuum/anaconda/envs/py3k/lib/python3.4/site-packages/quaternion/", line 3, in <module>
>     from .numpy_quaternion import quaternion
> TypeError: __import__() argument 1 must be str, not bytes
> The only thing before that line is `import numpy as np`, which typically works just fine.  Obviously, I'm using python3.4 to compile and (attempt to) import (with a conda environment), so it's not something as dumb as using the wrong python.  Also, this is the result for both me on my laptop and Travis-CI <>, so it doesn't seem to be anything peculiar to my installation.  I've posted this question on stackoverflow, but haven't gotten much interest; the only responder suggested I ask here instead.
> Any ideas what's going wrong, or where I can go from here?

I question whether the error is really coming from that particular
import line.  Try shadowing the __import__ function to see what's
actually being passed there.  E.g.:

>>> orig_import = __import__
>>> def debug_import(name, globals=None, locals=None, fromlist=(), level=0):
...   print("debug_import:", name, globals, locals, fromlist, level)
...   return orig_import(name, globals, locals, fromlist, level)
>>> import builtins
>>> builtins.__import__ = debug_import
>>> import sys
debug_import: sys {'__spec__': None, '__loader__': <class
'_frozen_importlib.BuiltinImporter'>, '__package__': None, 'builtins':
<module 'builtins' (built-in)>, 'orig_import': <built-in function
__import__>, '__builtins__': <module 'builtins' (built-in)>,
'__name__': '__main__', '__doc__': None, 'debug_import': <function
debug_import at 0x7f6096aac9d8>} {'__spec__': None, '__loader__':
<class '_frozen_importlib.BuiltinImporter'>, '__package__': None,
'builtins': <module 'builtins' (built-in)>, 'orig_import': <built-in
function __import__>, '__builtins__': <module 'builtins' (built-in)>,
'__name__': '__main__', '__doc__': None, 'debug_import': <function
debug_import at 0x7f6096aac9d8>} None 0

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